High Levels Of Fecal Coliforms Research Articles

Fecal coliform assessment and detection of blaTEM, blaSHV, and tetA in Escherichia coli isolated from selected river waters of Tacloban City, Leyte, Philippines

Fecal coliforms (FCs) are generally used as indicators of fecal pollution in water systems. High levels of FC pollution in water bodies may also be associated with antibiotic resistance. Escherichia coli, a member of the FC group, is generally commensal and harmless. However, some strains can cause various diseases in humans. The prevalence of antibiotic-resistant E. coli has been reported in several river systems worldwide. Herein, we report the most probable number (MPN) of FC and E. coli and the first detection of blaTEM, blaSHV, and i>blaSHVetA antibiotic resistance genes (ARGs) as well as ARG combinations (i.e. blaTEM + tetA and blaSHV + tetA) in E. coli isolates from river waters with high levels of FC in Tacloban City. MPN was determined using a multiple-tube fermentation technique, and ARG was detected using polymerase chain reaction (PCR). Results show that the Bagacay River had the highest MPN of FC and E. coli (both >160,000 MPN/100 mL), followed by the Burayan Creek (>160,000 MPN/100 mL; 160,000 MPN/100 mL), the Mangonbangon River (92,000 MPN/100 mL; 54,000 MPN/100 mL), and the Tigbao River (35,000 MPN/100 mL; 24,000 MPN/100 mL). Among the 113 uidA gene-confirmed E. coli isolates, blaTEM, blaSHV, and tetA were detected in 39 (34.5%), 7 (6.2%), and 83 (73.5%) E. coli isolates, respectively. Moreover, 34 (30%) of the isolates possess both blaTEM and tetA, and five (4.4%) of the isolates have both i>blaSHV and tetA. These results imply that the rivers are unsafe for anthropogenic use and the presence of ARGs in E. coli isolates pose a threat for locals. Hence, the public is urged to ensure safety and awareness in relation to these water environments. Further monitoring and source tracking are recommended to enhance environmental and public health safety among locals.

Assessment of the effectiveness of a full-scale trickling filter for the treatment of municipal sewage in an arid environment: Multiple linear regression model prediction of fecal coliform removal

In response to water scarcity, Morocco faces the challenge of using treated wastewater for irrigation purposes. This study evaluates the efficiency of a full-scale trickling filter (TF) system in Imintanout, Morocco. The system consists of three septic tanks, two TFs, and secondary decanters. Over a 5-year period, the system showed significant reductions in pollutants: 98 % of TSS, 94 % of BOD5, 98 % of COD, 41 % of TP, and 88 % of NH4+, with these reductions being statistically significant at the 95 % confidence level. A multiple linear regression (MLR) model successfully predicted the removal of fecal coliform (FC) by the TF, and a reduction of 2.88 log units was achieved. High cos2 values indicated the importance of hydraulic loading rate (HLR), BOD5, and FC, which were particularly affected by seasonal variations. Positive correlations between FC and TSS in certain periods highlight the seasonal variability in the composition of urban wastewater, which is effectively captured by the MLR model (R2 = 0.77). Although the treated water complied with Moroccan discharge standards, its high nitrate (140 mg L−1) and FC (4.32 log units) levels made it unsuitable for reuse in agricultural and landscape irrigation, as they exceeded safety limits. This work highlights the importance of optimizing treatment systems to produce high quality reclaimed water, which is essential to meet the challenges of water scarcity.

Water Quality and Risk Assessment of Selected Heavy Metals in Tilapia Oreochromis niloticus from Pulangi Lake, the Philippines

Regular monitoring of the water quality and heavy metal concentration in edible fish from the Pulangi Lake – an artificial lake in Bukidnon, the Philippines – has not yet been established. This study analyzed the water quality of the Pulangi Lake and assessed the associated risks of heavy metals cadmium (Cd), chromium (Cr), and lead (Pb) in Nile tilapia (Oreochromis niloticus) harvested from the lake during the dry season. Key informant interviews (KII) were also conducted to gather relevant information about the lake. The physico-chemical analysis of the surface water revealed high fecal coliform levels, exceeding the standard limit by more than 100%, but the concentrations of Cd, Cr, and Pb were below the standard limit. However, the Cr concentration in tilapia (0.2430–1.7870 mg/kg) exceeded the permissible limit of 0.05 mg/kg set by the Food and Agriculture Organization and the World Health Organization. Low concentrations of Cd (0.0270–0.1140 mg/kg) and Pb (0.0360–0.4350 mg/kg) were observed. The risk assessment of these individual heavy metals measured from tilapia and its combined impacts showed no potential non-carcinogenic effects based on the estimated target hazard quotient (THQ < 1) and hazard index (HI < 1). However, based on the permissible target cancer risk (1 x 10–6 to 1 x 10–4), tilapia from the Pulangi Lake should be reexamined as it appears that – in terms of Cd and Cr – the probability relating to contamination problem can occur. The present study can be used as baseline data for risk management.

Microbiological Quality and Heavy Metal Concentrations in Slipper Oyster (Crassostrea iredalei) Cultured in Major Growing Areas in Capiz Province, Western Visayas, Philippines: Compliance with International Shellfish Safety and Sanitation Standards

The increasing demand for slipper oyster (Crassostrea iredalei) has propelled farmers to expand oyster cultivation areas in the Philippines, chiefly for local consumption and feasibly for export overseas. As filter feeders, oysters can accumulate pathogens from the surrounding waters, and these pathogens can cause foodborne diseases in consumers. Therefore, oyster farming areas must be monitored for microbiological quality and heavy metal concentrations. In the present study, the microbiological quality of oysters and their growing waters in the major oyster farming areas of the Cogon and Palina Rivers and Cabugao Bay (in Roxas City and the Municipality of Ivisan, respectively, Capiz Province, Western Visayas, Philippines) were examined monthly during the wet (May to October) and dry (November to April) seasons over 12 months. Regardless of the sampling period, high levels of fecal coliforms in the water and Escherichia coli in oysters were found, clearly illustrating that these oyster growing areas would meet only the class B standard under the European Union classification system and would be considered "prohibited" for growing oysters under the U.S. classification system. Although Salmonella was occasionally detected in oysters, Vibrio cholerae was not detected and Vibrio parahaemolyticus was within acceptable limits. The heavy metal concentrations in oyster meat were also determined during the wet (July) and dry (March) seasons. Zinc and copper were the most abundant metals detected, and concentrations of lead, cadmium, mercury, and chromium were below the regulatory limits set by the European Union and the U.S. Food and Drug Administration. These oyster culture areas should be rehabilitated immediately to improve the microbiological quality of the oysters. Oysters harvested from these sites must be depurated or relayed to ensure quality and safety.

Quality assessment of water intended for human consumption from Kwanza, Dande and Bengo rivers (Angola)

Angola is one of the countries with a high rate of waterborne diseases, due to the scarcity and poor quality of water for human consumption. The watercourses are receptors of many effluents, mainly domestic sewage, due to a precarious or inexistent sanitation system and a small number of wastewater treatment plants. Therefore, this study aims: (i) to evaluate the water quality (physicochemical and microbiological parameters) of three Angolan rivers (Kwanza, Bengo and Dande) in locations where water is used as drinking water or abstracted for human consumption; (ii) to develop a new water quality index able to quantitatively express the water quality in those sites; and (iii) to assess the spatial distribution of water pollution through principal component analysis (PCA).Water quality assessment was performed by conducting four field surveys (campaigns I to IV); the first two campaigns took place in the dry season, while the last two ones took place in the rainy season. In the first two campaigns, the water quality was suitable to be treated for the production of drinking water, while in the last two campaigns, the water was unsuitable for that purpose (high levels of faecal coliforms were detected). The water quality index allowed to classify the water as generally excellent (campaigns I and II) and poor (campaigns III and IV). The rudimentary disinfection usually performed by individual water suppliers may improve the water quality, but it was not enough to achieve the parametric values required for human consumption in the rainy season (campaigns III and IV) except for Bengo sites. PCA identified sampling sites with the same water quality patterns, grouping into four groups (Kwanza sites) and two groups (Dande and Bengo sites). Therefore, the results of this study may support decision-makers as regards water supply management in the river stretches under study.The new developed Water Quality Index can support decision-makers in terms of water supply management, especially in countries with a high rate of waterborne diseases (e.g. Angola).

Evaluación de la calidad de agua de ríos de colombia usando parámetros físicoquímicos y biológicos

Se analizaron las características físicas, químicas y microbiológicas (coliformes totales, coliformes fecales y macroinvertebrados acuáticos) de diversos ríos de Colombia y se determinó el índice de calidad de agua (IQA) de los ríos estudiados. Se encontraron altos niveles de turbiedad y sólidos disueltos totales (SDT) sugiriendo que el agua de los ríos de Colombia no posee condiciones óptimas para el crecimiento y la reproducción de diversos organismos acuáticos. Además, se encontraron altos niveles de coliformes fecales, asociado con la existencia de vertimientos de aguas residuales, indicando que gran parte del agua de los ríos de Colombia, no es apta para consumo humano. Además el índice de BMWP/Col. correspondió a aguas ligeramente contaminadas y el Índice de calidad de agua (IQA) sugirió un recurso hídrico altamente contaminado, existiendo congruencia entre los dos índices anteriormente mencionados y algunas variables fisicoquímicas y biológicas, que presentaron valores superiores a los permisibles establecidos por la normatividad Colombiana

Reflex of urban space changes and climate conditions in Biomphalaria glabrata population dynamics on potential schistosomiasis foci in northeastern Brazil

To understand better the space-disease process of urban schistosomiasis mansoni in northeastern Brazil, this study assessed four sites considered to be potential foci. Molluscs were collected monthly between January to December 2010, were assessed for species and infection, quantified, and measured; rainfall data were obtained; and water samples were analysed for faecal coliform. The specimens collected were identified as Biomphalaria glabrata . At all sites, we observed high levels of faecal coliforms. The sanitation projects within the Coqueiral and Japaozinho neighbourhoods positively influenced population of B. glabrata . A similar phenomenon occurred in the Soledade neighbourhood, where a portion of the study site was excavated for building construction. The population of molluscs and positivity increased during the rainy season whereas mmolluscs size was differently influenced by rainfall. Rainfall combined with anthropogenic activity influenced foci dynamics during the study period, indicating that schistosomiasis is well-established in the Aracaju urban environment, primarily due to the ability of Biomphalaria to adapt to manmade changes associated with precarious sanitation.

Assessing the sources of high fecal coliform levels at an urban tropical beach.

Recreational water quality is commonly assessed by microbial indicators such as fecal coliforms. Maceió is the capital of Alagoas state, located in tropical northeastern Brazil. Its beaches are considered as the most beautiful urban beaches in the country. Jatiúca Beach in Maceió was found to be unsuitable for bathing continuously during the year of 2011. The same level of contamination was not observed in surrounding beaches. The aim of this study was to initiate the search for the sources of these high coliform levels, so that contamination can be eventually mitigated. We performed a retrospective analysis of historical results of fecal coliform concentrations from 2006 to 2012 at five monitoring stations located in the study region. Results showed that Jatiúca Beach consistently presented the worst quality among the studied beaches. A field survey was conducted to identify existing point and non-point sources of pollution in the area. Monitoring in the vicinity of Jatiúca was spatially intensified. Fecal coliform concentrations were categorized according to tide range and tide stage. A storm drain located in northern Jatiúca was identified as the main point source of the contamination. However, fecal coliform concentrations at Jatiúca were high during high tides and spring tides even when this point source was inactive (no rainfall). We hypothesize that high fecal coliform levels in Jatiúca Beach may also be caused by aquifer contamination or, more likely, from tide washing of contaminated sand. Both of these hypotheses will be further investigated.

Climate relationships to fecal bacterial densities in Maryland shellfish harvest waters

Coastal states of the United States (US) routinely monitor shellfish harvest waters for types of bacteria that indicate the potential presence of fecal pollution. The densities of these indicator bacteria in natural waters may be related to climate in several ways, including through runoff from precipitation and survival related to water temperatures. The relationship between interannual precipitation and air temperature patterns and the densities of fecal indicator bacteria in shellfish harvest waters in Maryland's portion of the Chesapeake Bay was quantified using 34 years of data (1979–2013). Annual and seasonal precipitation totals had a strong positive relationship with average fecal coliform levels (R2 = 0.69) and the proportion of samples with bacterial densities above the FDA regulatory criteria (R2 = 0.77). Fecal coliform levels were also significantly and negatively related to average annual air temperature (R2 = −0.43) and the average air temperature of the warmest month (R2 = −0.57), while average seasonal air temperature was only significantly related to fecal coliform levels in the summer. River and regional fecal coliform levels displayed a wide range of relationships with precipitation and air temperature patterns, with stronger relationships in rural areas and mainstem Bay stations. Fecal coliform levels tended to be higher in years when the bulk of precipitation occurred throughout the summer and/or fall (August to September). Fecal coliform levels often peaked in late fall and winter, with precipitation peaking in summer and early fall. Continental-scale sea level pressure (SLP) analysis revealed an association between atmospheric patterns that influence both extratropical and tropical storm tracks and very high fecal coliform years, while regional precipitation was found to be significantly correlated with the Atlantic Multidecadal Oscillation and the Pacific North American Pattern. These findings indicate that management of shellfish harvest waters should account for changes in climate conditions and that SLP patterns may be particularly important for predicting years with extremely high levels of fecal coliforms.

English

The study investigates the effects of Eichhornia crassipes (water hyacinth) infestation based on coliform loads which are pollution indicator organisms. These dams have fish and the waters are commonly used for domestic purposes without any treatment hence it is necessary to check their status. Sampling was done on 25 small water bodies and from which water samples were taken for microbial determination. Membrane filtration method was used to enumerate fecal coliforms by use lauryl sulphate broth and incubated at 44 ± 0.5°C for 18 to 24 h. The results show that water bodies infested by water hyacinth harbored higher levels of fecal coliforms compared to those devoid of the weed. The high fecal coliform levels have negative impacts on the lives of communities using these water bodies. In addition, it reduces native species and disrupts food chains and nutrient cycle. The small water bodies within the Lake Victoria basin need frequent monitoring in order to give the relevant authorities concrete information for proper sensitization to the communities. Water hyacinth should also be properly managed so that it does not chock dams that are used for domestic and fishing activities. Key words:  Coliform load, infestation, pollution, local community, Eichhornia crassipes.

Assessment of the Water Quality of Buhisan, Bulacao and Lahug Rivers, Cebu, Philippines Using Fecal and Total Coliform as Indicators

This study was conducted to evaluate and compare the water quality of Buhisan, Bulacao and Lahug rivers in Cebu, Philippines using coliforms as indicators. Monthly sampling started from November 2011 to April 2012 in the upstream, midstream and downstream stations. The multiple tube fermentation technique was used for the analysis of coliforms. High total and fecal coliform counts were observed in the three rivers from February to April, but the difference in values across time was not significant. Fecal coliform counts of Buhisan and Bulacao rivers differed significantly across sampling stations. This was most likely due to the low fecal coliform (FC) values in the upstream compared with the midstream and downstream. The generally high FC and TC levels throughout the sampling period confirmed the presence of fecal pollution in the rivers. Organic pollution and the presence of coliforms could be related to the accumulation of wastewater due to high impact human activities across the river networks. It is therefore recommended to conduct an inventory and monitor non-point sources of water pollution, establish wastewater treatment measures and enforce policies for river protection.

가막만해역 해수의 세균학적 수질 평가

From 1998 to 2008, the bacteriological quality of seawater in Kamak Bay, Korea, was monitored. The total and fecal coliforms in seawater were monitored as bacterial indicators, and the level of fecal coliform contamination was used to evaluate seawater quality. In the southern shellfish growing area of Kamak Bay, the observed fecal coliform geometric mean (GM) and estimated 90th percentile did not exceed the quality standards for fecal coliforms in seawater in Korea and th USA (GM<14 MPN/100 mL, 90th percentile<43 MPN/100 mL). The GM and estimated 90th percentile of the fecal coliform levels in the adjacent northern area of Kamak Bay were higher than in the southern area. Stations near wastewater discharge sites and urban areas in the north had the lowest quality and did not meet the bacteriological seawater quality criteria. The high fecal coliform levels in the Seonso coastal region near wastewater discharges and northern urban areas declined significantly following dredging and operation of a sewage treatment plant.

Effects of water management on hydrology and water quality of a semi-arid watershed in the Northeast of Brazil

Water resource management based on dam construction, diversion, and other engineered hydraulic structures improves conditions for humans living in arid and semi-arid areas. However, the effects of damming on fluvial and coastal ecosystems are well-know, as it is the fact that economic and social development based on water management might enhance the pressure on such environments. This study gives a first basin scale representation of the possible effects of water resource management on hydrology and water quality of a typical semi-arid watershed/ estuarine system in Northeastern Brazil. Although the dam cascade suggests a hydrological alteration of the stream flow, the upstream location of dams in the Coco watershed does not apparently alter the total discharge to the estuary. Water quality threats, such as high fecal coliform levels and low dissolved oxygen indicated that although water management supported extensive economic and social development, it resulted in considerable degradation of aquatic systems if no attention was paid to environmental and sanitary conditions.

Methods for Quantifying Lime Incorporation into Dewatered Sludge. I: Bench-Scale Evaluation

The addition of alkaline material (usually lime) to treated municipal sludge can be used to raise the pH to ⩾12 and generate Class A or B biosolids. When lime is added to dewatered sludge, it must first be made into a slurry before the pH can be measured to demonstrate regulatory compliance. In this study, pH 12 was achieved in slurries prepared from lime-amended dewatered sludge, even when the lime was poorly incorporated and relatively high fecal coliform levels were detected. Thus, quantitative indicators of lime incorporation are needed to complement slurry pH measurements and ensure that sufficient contact occurs between lime and sludge particles to achieve adequate stabilization. In this study, the usefulness of several potential measures of lime incorporation—pH, CO2 consumption, distribution of calcium, fecal coliforms, NH3 and reduced sulfur compound production, and ATP—was systematically evaluated using a bench-scale system. Sludge pH and CO2 consumption were not influenced by the extent of lime incorporation. The distribution of calcium and fecal coliform levels appear to be useful measures of lime incorporation. NH3 and reduced sulfur compound emissions and ATP levels can also be used to assess lime incorporation provided recommended experimental techniques are used.

Occurrence of Staphylococcus and enteropathogens in soft cheese commercialized in the city of Rio de Janeiro, Brazil.

To investigate the presence of Staphylococcus aureus, enteropathogenic Escherichia coli (EPEC), Aeromonas spp. and Yersinia spp. in soft cheese commercialized in Rio de Janeiro, Brazil. A total of 45 samples of cheese from three different brands marketed in Rio de Janeiro city were analysed for faecal coliform levels using the Most Probable Number (MPN) technique. The samples were also analysed using conventional methodology for the investigation of food-borne pathogens. High levels of faecal contamination were detected in 95.5% of cheese samples. Staphylococcus aureus was isolated from 20% of samples, of which 17.7% were above the limits allowed by Brazilian legislation. Aeromonas hydrophila and Aer. caviae were detected in 17.7% of the samples. Yersinia spp. were not found in this study. EPEC was isolated from 21.1% of the samples and the most frequently found serogroups were O127, followed by O55 and O26. Our results showed that 95.5% of cheese samples had high levels of faecal coliforms. The isolation of Staph. aureus, serogroups of EPEC and Aeromonas spp. suggested that the soft cheese commercialized in the city of Rio de Janeiro may represent a health risk for the consumers. These results suggest that soft cheese may act as an important vehicle of transmission for well-established pathogens.

Identification of the sources of fecal coliforms in an urban watershed using antibiotic resistance analysis

Bacteria such as fecal coliforms are used as indicators of fecal pollution in natural waters. These bacteria are found in the feces of most wild and domestic animals and thus provide no information as to the source of fecal contamination, yet identification of indicator bacteria sources allows improved risk assessment, remediation, and total daily maximum load (TDML) assessment of environmental waters. This bacterial source tracking study was initiated in order to identify the dominant source(s) of fecal contamination in the urban watershed of Stevenson Creek in Clearwater, Florida. Five sites that represent areas where routine monitoring has previously shown high levels of fecal coliforms were sampled over 7 months. Fecal coliforms were enumerated by membrane filtration, and antibiotic resistance analysis was used to “fingerprint” a subset of randomly selected isolates and statistically match them to fingerprints of fecal coliforms from known sources (the library). A field test of the classification accuracy of the library was carried out by isolating fecal coliforms from the soil and waters surrounding a failing onsite wastewater treatment and disposal system (OSTDS). The vast majority of the isolates were classified into the human category. The major sources of fecal pollution in Stevenson Creek over the course of the study were wild animal, human, and, to a lesser extent, dog. Overall, wild animal feces were identified as the dominant source when fecal coliform levels were high, but when fecal coliform levels were low, the dominant source was identified as human. The results of this study demonstrate that the sources of fecal indicator bacteria within one urban watershed can vary substantially over temporal and spatial distances.

Nutrient and faecal contamination and retention in wetland enclosures (gei wais) in the Mai Po Marshes, Hong Kong

Nutrient and faecal contamination is an increasing problem to the shrimp productivity and wildlife conservation at the internationally important wetland ecosystems of the Mai Po Marshes (Hong Kong, P.R. China). The present study examined the nutrient status and faecal bacteria loading and potential retention capacity of contaminants of two wetland enclosures. Water in the wetland enclosures was eutrophicated with high concentrations of dissolved inorganic nitrogen (inorg–Ndiss= 15.0 mg l−1) and orthophosphate phosphorus (o-P = 1.89 mg l−1) and was loaded with high levels of faecal coliforms (172 ×103 cfu in 100 ml) and faecal streptococci (1.94 ×103 cfu in 100 ml). The pattern of nutrient enrichment of two wetland enclosures is related to a north-to-south pollution gradient from the Shenzhen River to the wetlands. By retaining tidal water in the wetland for an 8-day period, water quality was greatly improved; NH4–N was removed by 83%, o-P by 45% and faecal bacteria by 100%. This implies a self-purification capability of the wetland enclosures and a potentiality of using them as an alternative sewage treatment.

Growth of indicator bacteria in a flow-through aquaculture facility

A flow-through commercial catfish growout operation was found to have high levels of fecal coliforms (FC) in the discharge. Analyses by academic, commercial and regulatory agency laboratories were conducted through the system over a five month period in 1991 for various indicator bacteria groups as well as potential pathogens with highly variable results. Biochemical differentiation of FC showed most to have been Klebsiella pneumoniae, K. oxytoca, E. coli and Citrobacter freundii. During production many of the effluent FC levels exceeded state surface water criteria for contact and non-contact recreation of 200/100 ml. Generally, great diversity in results were shown between laboratories depending on their analytical specialty and whether they were responding to requests to show the FC populations to have been fecal in origin, or potential pathogens.

An outbreak of Norwalk‐like gastroenteritis associated with contaminated drinking water at a caravan park

During the 1989 Christmas holiday period, a large outbreak of gastroenteritis occurred among persons staying at a caravan park in southern New South Wales. Review of local hospital records found that 77 per cent of patients presenting with infective diarrhoea between 29 December and 3 January had stayed at the caravan park. In a retrospective cohort study we compared rates of illness among caravan park patrons exposed to different water sources. Stools were tested for pathogens and convalescent sera for viral antibodies. Rain and reticulated river water sampled from the caravan park were tested for bacteria and viruses. Of 351 persons interviewed at the caravan park, 305 (87 per cent) reported an illness characterised by diarrhoea, vomiting and abdominal pain. Of 196 persons who used reticulated river water for drinking or ablutions, 175 (89 per cent) became ill compared with 47 of 72 persons (65 per cent) who did not use this water (relative risk 1.4, 95 per cent confidence interval 1.2 to 1.6). The outbreak was probably caused by a 27-28 nm small round structured virus found in the stool from one ill person. High levels of faecal coliforms in the reticulated river water and enterovirus in sediment samples suggest that the outbreak was caused by sewage contaminating the reticulated river water through a break in the pipe directly over the underground water tanks. To prevent such outbreaks, poor water and sewerage system layouts should be avoided and nonpotable water should be clearly labelled. Where feasible, all camping-ground water should stem from town supplies.

Current and possible alternate indicators of fecal contamination in tropical waters: A short review

AbstractBacteria that belong to the total and fecal coliform groups have been used for several decades as indicators of fecal pollution of waters and other systems. The prevailing idea behind this is that these two groups of bacteria cannot replicate outside the gastrointestinal tract of warm‐blooded animals. Several studies conducted by this and other laboratories have indicated that these bacteria may be naturally present in certain areas of the world. Naturally occurring fecal coliforms (the genera Escherichia and Klebsiella) have been isolated from pristine sites and from sites where there was no apparent fecal contamination. All these results lead us to the conclusion that these groups of bacteria are not adequate indicators of fecal contamination in tropical areas of the world. Alternate indicators are being tested. This laboratory and others around the world are testing the adequacy of bacteriophages (more specifically, coliphages) for this purpose. In Puerto Rico coliphages have been detected only in areas known to be contaminated with domestic sewage, but not in pristine areas, although high levels of fecal coliforms can be detected at the latter sites. All these results suggest that coliphages may be used as indicators that more realistically demonstrate fecal contamination of waters in tropical areas of the world. In addition, newer techniques, although still in the trial stages, can be used to directly detect pathogens in the environment. Of all the techniques currently available, the polymerase chain reaction is the most promising for the direct detection of pathogens and therefore for the unequivocal evaluation of the biological quality of waters.